This invention relates to a process for producing nitric acid and, more particularly, to a process for treating a fluid stream carrying various components including nitrogen oxides, wherein the stream is subjected to oxidative reactions under gaseous and absorptive conditions to convert a portion of the nitrogen oxides to nitric acid and thereby simultaneously reduce the concentration of nitrogen oxides in the stream discharge.
Prior processes and apparatus have been provided for the production of nitric acid, as, for example, from a fluid stream produced in an ammonia combustion process.
In the conventional prior process, as shown in U.S. Pat. No. 2,134,733, RICHARDSON, an oxidization step and an absorption step are utilized to produce nitric acid from the off gas through an ammonia oxidization step wherein the fluid emitted from the ammonia oxidization step is passed through a separator and where the off gas from the oxidization step passes through the absorber. Liquid product nitric acid is removed from both the oxidizer means and the absorber. Liquid product nitric acid is removed from both the oxidizer means and the absorber means and the two product streams are mixed.
Another previous arrangement, as shown in U.S. Pat. No. 3,339,965, KALOUS, has provided multi-stage steps for the oxidization and separation of nitrogen oxides for the production of nitric acid from a fluid stream, for example, wherein the off gas of the fluid stream from an ammonia oxidization process and wherein the product from the ammonia oxidization step is separated and then dilivered to two different combined absorption and oxidization reaction means.
In another prior arrangement, as shown in U.S. Pat. No. 3,591,342, LEROLLE, the fluid stream emitted from an ammonia burner is first passed through a separator to separate its liquid and gas phases, while the liquid therefrom is passed immediately to the absorber, and no separator liquid is supplied to the oxidizer means. In the process taught by Lerolle, the product from the ammonia oxidization stream is supplied directly to the absorber and none of the liquid product from the ammonia oxidization process is applied initially to the oxidizer.